This is a phase II, randomized, ulticenter, double-blind, placebo controlled, parallel group, dose-response study of the pharmacodynamics, pharmacokinetics, safety and tolerance to trk-820 in patients with chf and hyponatremia. The specific aims AR L. To assess the renal, neurohormonal and systemic hemodynamic effects of trk-820 in chf patients; 2. To determine the acute effect of trk-820 on the dilutional hyponatremia of chr; 3. To determine the pharmacokinetics of trk-820 in patients with chf, and 4. To evaluate the safety of trk-820 in patients with chf.